Final answer:
In 'An Indian Father's Plea' by Robert Lake, the most effective rhetorical appeal used is Pathos, as it emotionally conveys the son's cultural learning experiences and the author's fears as a father.
Step-by-step explanation:
In Robert Lake's essay 'An Indian Father's Plea', the author effectively uses different rhetorical appeals to convince the teacher to reconsider his son's academic performance. However, the appeal that stands out the most is Pathos, where Lake describes his son's unique learning journey and appeals to the teacher's emotions. He relays his son's upbringing in a culturally rich environment and his consequent struggles within the mainstream educational system. Additionally, Lake uses plenty of emotional language to convey his own fears and concerns as a father, which can resonate with the teacher on a human level. While there are elements of Ethos and Logos within his essay, such as mentioning his own educational background and presenting logical arguments regarding the cultural differences in learning, it's the emotional connection that is most persuasive in this context.